This invention concerns covers for containment of noxious and odorous gases such as in sewage treatment facilities, and particularly the invention is directed to a hatch cover or access panel for access to a tank having such a fixed cover, particularly a cover formed of assembled aluminum extrusions.
A number of patents of Hallsten Corporation (Sacramento, Calif.) have described fixed covers for sewage treatment process tanks, pursuant to requirements for containing noxious and odorous gases against freely escaping into the atmosphere. See, for example, U.S. Pat. Nos. 5,941,027, 6,012,259, 6,151,835 and 6,802,157. In all the described fixed covers, the construction was of extruded aluminum slat components connected together by edges and by engaging in channels at ends of the slats. Where a liftable panel or hatch cover was provided, or where the fixed cover structure rested on a tank edge at the periphery of the tank, rubber gasket material was included to provide a substantial, if not total, gas seal.
Hinged hatches or access panels were provided in some of the fixed tank covers of the above-listed patents. These have typically been slide latches wherein a locking finger, when the slide member is moved to the locking position, would engage underneath a beam or other fixed structure adjacent to the movable, hinged panel. This, however, required some form of seal to be made around the slidable component, since the handle was available from above the hatch's seals and the latching finger was below. Such seals were imperfect and prone to leakage, and could not be relied on to contain gases from escaping.
It is an objective of the current invention to provide an improved slide bolt-type latch for a liftable access panel in a fixed tank cover, wherein the gas seal between the liftable panel and surrounding fixed structure is not compromised.